As is well known in the textile art, braiding machines utilize fiber carriers which are placed in motion in order to intertwine yarns to form a braided material. Multi-ply braiding machines typically use a matrix-like configuration of yarn carriers which move in alternate row and column position shifts. By reversing the movement of row and column motions of yarn carriers during operation of a braiding machine, the yarns are intertwined together to form a braided product, typically a complex shape not possible to manufacture by other types of textile processes.
As is also known in the textile art, three-dimensional braiding processes have become recognized for their advantage in fabricating integrated and near net-shaped preforms for advanced composite materials which are used, for example, in rocket nozzles and the like in the U.S. space program. Three-dimensional braiding has the capability of fabricating three-dimensional integrated structures, and also provides great ease in forming complex structural shapes. With three-dimensional braiding desired preforms can be directly fabricated into the nearly net shapes of the final products of the composite material by manipulating the relative positions of the individual yanks or fiber tows in the braiding machine bed. The technology has recently attracted a great amount of attention from various industries, including the aerospace industry, and made three-dimensional braided composite products a very active and prominent branch of advanced composite materials.
In view of the above, a significant research effort is underway to automate three-dimensional braiding processes in order to produce uniform, repeatable and cost-effective products therefrom. For example, in the School of Textiles at North Carolina State University a three-dimensional braiding laboratory is working toward developing automated three-dimensional braiding machines, including both four-step (Cartesian or Magna Weave) and two-step braiding apparatus.
With particular reference to automated three-dimensional braiding machines, researchers at North Carolina State University have discovered that large moving distances of the yarn carriers across the braiding machine bed are required, and thus a large rewinding or retraction capability for the yarn carriers is a necessity for the further development of this technology. It has further been discovered that yarn carriers with continuous yarn supply and retraction capability will have to be utilized in the three-dimensional braiding machines. Unfortunately, the yarn carriers which are presently available are capable of continuously supplying yarn but are unsatisfactory for three-dimensional braiding machines due to the fact that the rewinding lengths or retraction capability are very limited. In this regard see, for example, the yarn carrier disclosed in Heine U.S. Pat. No. 4,700,607.
Also, applicants are aware of a limited retraction braiding yarn carrier device manufactured by A. B. Carter Company of Gastonia, North Carolina, which comprises a yarn spool mounted directly on a spring motor which is adapted to tighten and then partially unwind by rotatably slipping within the carrier housing during continuous yarn supply. Although the device can provide a long continuous supply of yarn, the retraction capability is limited by the direct mounting of the yarn spool on the spring motor thereof.
Accordingly, a need has arise for such a yarn carrier apparatus which, while compact, will provide both continuous yarn supply and the requisite large rewinding lengths necessary for automated braiding machines as well as other suitable uses for such a yarn carrier apparatus. The yarn carrier apparatus of the present invention meets this need in view of its surprising yarn feeding and high retraction capabilities.